The present disclosure relates to a bone anchoring device comprising an anchoring element which has a shank to be anchored in a bone and a head having an exterior surface with a spherical segment-shaped portion, a receiving portion to receive said head and an element which exerts pressure on said head, wherein said shank and said head are separate parts.
A bone anchoring device of this type is known from U.S. Pat. No. 6,835,196 B2. The shank of the anchoring element has a cylindrical end portion which is received in a corresponding bore in the head which has a spring-yielding edge to clamp said end portion of the shank when pressure is exerted on the head. In another embodiment the end portion of the shank has an outer thread which cooperates with an inner thread of the bore in the head receiving said end portion. With this bone anchoring device it is possible to first screw in the shank, adjusting the length of the shank, if necessary, and then connecting it with the receiving portion containing the head.
U.S. Pat. No. 6,074,391 discloses a bone anchoring device comprising a bone screw having a threaded shank with a spherical section forming a free end of the shank. The bone anchoring device further comprises a receiving part having on the inner side a conically shaped annular surface converging downwardly. A slotted cage provided in the receiving part encompasses the spherical section and has an outer conically shaped surface which cooperates with the conical surface of the receiver part. The slots in the cage allow for the spherical section of the shank being clamped when pressure is exerted onto said cage.
WO 94/00066 discloses an osteosynthetic fixation device consisting of a securing component having a conical head section and an adjoining anchoring component designed for fixing in the bone and a spherical segment-shaped slotted clamping component with a conical bore to receive the conical head section to clamp inside a connecting component having a spherical segment-shaped bore. The clamping component has an outer surface with a spherical segment-shaped portion. The fixation of the securing component inside the connecting component is achieved by pulling the conical head section into the clamping component such that the clamping component is spread to press against the spherical segment-shaped bore of the connecting component.
U.S. Pat. No. 6,063,090 discloses a device for the connection of a rod with a pedicle screw which allows to first screw a screw element with a spherical head into the bone and thereafter to click a retainer head to be connected with the rod onto the spherical head. To fix the angular position of the screw element relative to the retainer head the spherical head is clamped by a conical spring chuck.